Encoding and decoding a self-clocking three-part data stream is discussed in U.S. patent application Ser. No. 206,407, "Three-Part Decoder Circuit" by Michael Lee Wash filed June 14, 1988, now abandoned; U.S. patent application Ser. No. 206,408, "Three-Part Encoder Circuit" by Arthur Allan Whitfield and Michael Lee Wash filed June 14, 1988, now U.S. Pat. No. 4,912,467, issued Mar. 27, 1990; U.S. patent application Ser. No. 206,553, "Three-Part Decoder Circuit" by Arthur Allan Whitfield filed June 14, 1988, now U.S. Pat. No. 4,876,697, issued Oct. 24, 1989; and U.S. patent application Ser. No. 206,646, "Method For Modulating A Binary Data Stream" by Michael Lee Wash filed June 14, 1988, now abandoned, the disclosures of which are incorporated herein by reference.
Storing information magnetically on moving media involves encoding clock and data pulses in a fashion that provides a reliable decoding means. The encoding method generally defines the decoding means.
In three-part encoding, the polarity of the clock pulses are the opposite of the polarity of the data pulses. The scheme makes the decoding process easier than, for example, a data stream encoded using MFM. An additional problem with the three-part encoding scheme is knowing, in the decode mode, which polarity pulse represents a clock bit and which polarity pulse represents a data bit. Once the polarity of pulses has been established, the decode process becomes trivial.